Lifting systems for association with various types of conveyors, for example roller conveyors, are often used to raise goods. These systems are so arranged that they receive goods from the rollers of the receiving conveyor, raise them on a higher level of the delivery conveyor for transfer to the delivery conveyor, typically at right angles to the receiving conveyor. Such systems usually have a base frame and a raisins element which can be shifted with respect to the base frame. A drive source is provided which is coupled to rotatable lifting elements which, for example, are a lever arrangement, and are coupled to the raising frame. The lifting system, thus, permits removal of goods from a receiving conveyor and transfer to the delivery conveyor at another level.
Usually, the lifting system has a raising element which, often, is in the form of a frame which is coupled to an intermediate element. The intermediate element, in turn, receives a short-stroke vertical raising movement, when driven by a suitable drive motor. One such lifting system uses a raising drive with rotating eccentric rollers which, always in pairs, are located, spaced next to each other, on parallel shafts which are rotatably journalled in the base frame. The raising elements, formed as U-shaped raising levers, are located in pairs at two opposite sides of the raising frame. The horizontal alignment of this arrangement, that is, the maintenance of a horizontal plane of the raising frame, must be reliably ensured and, to do so, it is necessary that the four raising rollers operate in precise synchronism. In one such structure, the shafts which carry the eccentric rollers are coupled via two gear drives, which may be angular drives, to a third shaft so that they are synchronized with respect to each other and form a continuous complete drive chain. This construction is complex, heavy, and requires, further, vertical slide or guide ways and shoes sliding thereon for vertical guidance of the lifting frame.
Another type of raising system also uses four eccentric rollers which are, in pairs, on two parallel shafts rotatably journalled in the frame. The two shafts are coupled via a sprocket chain or gear belt drive. The drive motor is coupled via a sprocket chain or gear belt to one of the two shafts. Sprocket chains or gear belts do not operate without play, and thus the raising system does not run smoothly, particularly in those portions of the raising or lowering cycle in which there is a reversal of direction of movement of the frame, that is, at the upper and lower terminal or end position.
Rather than using the center rollers, crank systems and crank disks or wheels have also been used as raising elements, the crank disks or wheels being located outwardly of the mechanical structure.
Another type of raising system uses four dual lever arrangements rather than rotating lifting arrangements such as eccenter rollers or cranks. Knee links are pivotably connected to the raising frame, and driven by a pneumatic or hydraulic raising cylinder. This construction also is complex and, for synchronous operation, requires careful and time-consuming adjustment and equalization.